The present application relates to manufacturing, and more specifically to apparatuses and methods for arranging fibers in particular shapes for use in creating composite preforms and products.
Fiber-reinforced composite materials, referred to herein as composites, are materials comprised of fibers embedded in a matrix material. Typical fibers include but are not limited to glass fibers, carbon fibers (e.g. graphite fibers and/or more exotic forms of carbon, such as carbon nanotubes), ceramic fibers, and synthetic polymer fibers, such as aramid and ultra-high-molecular-weight polyethylene fibers. Typical matrix materials include but are not limited to thermoset resins, such as epoxies, vinylesters, and polyurethanes and thermoplastic resins, such as polyamides and PEEK (PolyEther Ether Ketone), as well as other non-plastic materials such as metals and ceramics.
Composite materials often combine high-strength and relatively light weight. In typical composite products, the fibers provide high tensile strength in one or more directions and the matrix material hold the fibers in a specific shape. A set of fibers roughly in the shape of a final product is referred to as a preform. Preforms are comprised of layers of woven or non-woven fabrics, each of which is cut and arranged into a desired shape. Each cut fabric piece is referred to as a ply. Multiple plies of varying shapes and fabric types are often stacked in different orientations to provide strength and stiffness optimized for the intended usage of the final product.
Plies may be assembled into a preform, which is a fabric shape approximating the shape of the desired part. The preform may be fabricated outside of the mold or other rigid structure, and then placed as a unit within the mold or other rigid structure for molding. Alternatively, individual plies may be assembled inside or on a mold, mandrel, plug, or other rigid structure in the shape of the desired finished part. The process of assembling a preform or placing plies within a mold is referred to as layup.
Following the layup of a preform and/or plies, the plies may be solidified into a rigid part by adding and/or activating a matrix material. A matrix material, such as uncured polymer resin, may be embedded in the fabric prior to cutting plies (referred to as a pre-impregnated or prepreg material) or applied to or infused into the fabric during or after the fabric layup process, using processes including but not limited to such as wet layup, wet compression molding, or vacuum and/or pressure assisted resin transfer molding. The matrix material is then cured or hardened, often under elevated temperature and/or pressure differentials to ensure even distribution of the matrix material and prevent voids, air bubbles, or other internal defects. Pressure, heat, and/or electromagnetic energy, such as ultraviolet light or microwave energy, may be applied to the composite part during curing using techniques including but not limited to compression molding, vacuum bags, autoclaves, inflatable bladders, and/or curing ovens.
However, use of conventional fiber cloth and associated cloth-forming and preform-construction techniques can be particularly expensive due to waste and processing steps. Weaving or binding fibers into fabric adds substantial costs on top of the fiber costs. After cutting, there are often substantial amounts of scrap fabric that are too small and/or irregularly shaped to be useful. This waste cost is exacerbated if the fabric includes pre-impregnated matrix material. Furthermore, the optimal arrangement or nesting of plies for cutting is often different than the arrangement or order required for layup; therefore, additional labor or automation costs are required to collate cut plies into the correct layup quantities and order, referred to as kitting.
Additionally, it is often difficult to conform flat fabrics to curved shapes due to the stiffness, inelasticity, and resistance to shearing of the fabric material. Additionally, it is difficult to conform fabric to some types of non-planar (e.g. curved) shapes due to characteristics of the shape itself, such as regions of non-zero Gaussian curvature. These difficulties conforming fabric can lead to additional layup costs and material waste.